migrate files from `qiskit-ibm-runtime` to `Qiskit/docs` and convert `.rst` files to `.mdx`

[javabster]

@abbycross @beckykd I'm so lost with these pages pls help 😅

The following files should be migrated from the qiskit-ibm-runtime repo to this repo.

### Files to migrate to docs/start
- [ ] ~https://github.com/Qiskit/qiskit-ibm-runtime/tree/main/docs/migrate (convert to `.mdx`) - DISCUSS: is this content already covered in the migratiion files?~

### Files to migrate to docs/build

### Files to migrate to docs/test

### Files to migrate to docs/run

### Files to migrate to docs/optimize

### Files to migrate to docs/other
- [ ] https://github.com/Qiskit/qiskit-ibm-runtime/tree/main/docs/faqs (convert to `.mdx`)

---

DISCUSS:

• what should be done about runtime tutorials that are in the learning app? some tutorials like this one and this one seem more like documentation pages? what is the line between a 1docs page and a tutorial?
• should we move over the cloud folder?

[beckykd]

I'll walk through all of the runtime pages this afternoon. But No, we shouldn't move over the Cloud folder, Yes, the information in the Migration files is already covered in 1xp. These were some victims of the idea that we just needed fewer topics in the left hand nav, so they've been squashed together. We could pull them back apart if we want. My guess is that the vast majority of the files in Runtime are in 1xp, but we'll need to carefully compare the content for updates.

Update: I verified that every file that should be migrated to 1xp has already been migrated. I put them in a table if you're interested. I have not done a close compare yet though.